Thanks for the input, Petro. I already have olympic weightlifting shoes and I will continue working on mobility.
Kronos, I think it has something to do with the rapid descent and bounce at the bottom of the squat perhaps causing a sudden contraction. I feel it mainly in the lateral part of my calf.

Started getting pain in my left calf after I switched to high bar. At first I thought it was just DOMS but it hasn't subsided, in fact it has gotten worse. It almost impedes the contraction of the muscle and I really have to focus on shoving my knees out and driving up evenly but luckily with heavy weight it is not my main focus.
I believe the lifters at Average Bros gym refer to the pain as "calfitis". Have you guys had any experiences with it?

On my last squat session I was more focused on my form and perhaps what I'm calling hip drive is me keeping everything tighter on the way up and not let my hips sort of cave in. After switching to high bar I think I just started quadding the weight up and paying more attention to my hips helped to sort of even everything out.

@FerrousMaverick
Yes, Mike didn't actually learn that squat form from Rip, he just stated that just happens to be the way he squats.
I definitely agree with the idea of finding the technique that suits you. I've seen different powerlifters like Joe Morrow looking right up at the ceiling, Kyle Keough at one point had a ridiculously narrow stance and Ben Rice has a lot of forward lean in his squats.
I've watched many low and high bar squat tutorials with no special mention of driving up your hips. Although I have heard the cue of driving up into the bar a few times, for me it just doesn't seem to be very effective. I believe it was Dave Tate that said that squats are personal, you have to find the style that suits you.

After switching to a high bar squat I have recently become more aware of using my hips in the squat or "hip drahv" as I had done previously with low bar. This prompted me to post up some of the information I have found on the topic in general. Feel free to add your thoughts to to topic or any corrections if you think I have missed something.
I'm sure most people have already seen this video: (
), of Rippetoe coaching the squat and is where I think most people really get an idea of what he means.While this is helpful in understanding hip drive, for me it resulted in driving the hips back and performing a sort of good morning out of the squat. This is what is discussed in this video: ( http://www.youtube.com/watch?v=GynDZgEB1U0 )
For myself, as the weight got heavier I learned to use hip drive properly and not to over exaggerated pushing the sacral area up.
But for anyone is currently having problems with hip drive I've found that the best cue is to simply imagine getting up from a chair (which is the whole point of the box squat).
Another cue I have found useful for myself is to contract your glutes when coming out of the hole.
All 3 cues are essentially the same and I try to keep them in mind for coming out of the bottom of the squat.
Lifters I have found using Rippetoe's squat form and exhibiting great hip drive are Ben Rice and Michael Tuchscherer.
Also as discussed in this video: (
), as well as keeping your whole body tight to create a sort of "coiled spring" effect, you should really focus on pulling your self down with your hip flexors (causing you to descend slowly), which will give you greater explosiveness when using hip drive. Your hips will be probably be extremely sore after doing this and you might have to stretch a lot afterwards.
Some instructors such as in this video: (
), say you should not use hip drive during high bar squats but I have found it to be necessary.
Here is a video from California Strength: (
). You can hear someone cueing her to use her hips.
In this video you can see the lifter using his hips to come out of the hole: (
)
Also this video: (
). At 0:16 the lady in the pink top is a great example of using your hips)